title: Role of CB2 cannabinoid receptors in the rewarding, reinforcing, and physical effects of nicotine.
abstract: This study was aimed to evaluate the involvement of CB2 cannabinoid receptors (CB2r) in the rewarding, reinforcing and motivational effects of nicotine. Conditioned place preference (CPP) and intravenous self-administration experiments were carried out in knockout mice lacking CB2r (CB2KO) and wild-type (WT) littermates treated with the CB2r antagonist AM630 (1 and 3 mg/kg). Gene expression analyses of tyrosine hydroxylase (TH) and α3- and α4-nicotinic acetylcholine receptor subunits (nAChRs) in the ventral tegmental area (VTA) and immunohistochemical studies to elucidate whether CB2r colocalized with α3- and α4-nAChRs in the nucleus accumbens and VTA were performed. Mecamylamine-precipitated withdrawal syndrome after chronic nicotine exposure was evaluated in CB2KO mice and WT mice treated with AM630 (1 and 3 mg/kg). CB2KO mice did not show nicotine-induced place conditioning and self-administered significantly less nicotine. In addition, AM630 was able to block (3 mg/kg) nicotine-induced CPP and reduce (1 and 3 mg/kg) nicotine self-administration. Under baseline conditions, TH, α3-nAChR, and α4-nAChR mRNA levels in the VTA of CB2KO mice were significantly lower compared with WT mice. Confocal microscopy images revealed that CB2r colocalized with α3- and α4-nAChRs. Somatic signs of nicotine withdrawal (rearings, groomings, scratches, teeth chattering, and body tremors) increased significantly in WT but were absent in CB2KO mice. Interestingly, the administration of AM630 blocked the nicotine withdrawal syndrome and failed to alter basal behavior in saline-treated WT mice. These results suggest that CB2r play a relevant role in the rewarding, reinforcing, and motivational effects of nicotine. Pharmacological manipulation of this receptor deserves further consideration as a potential new valuable target for the treatment of nicotine dependence.
authors.affiliation: 1] Instituto de Neurociencias, Universidad Miguel Hernández (UMH)-CSIC, Alicante, Spain [2] Red Temática de Investigación Cooperativa en Salud (RETICS-Trastornos Adictivos), Instituto de Salud Carlos III, MICINN and FEDER, Madrid, Spain.
authors.forename: Francisco
authors.initials: F
authors.lastname: Navarrete
authors.forename: Marta
authors.initials: M
authors.lastname: Rodríguez-Arias
authors.forename: Elena
authors.initials: E
authors.lastname: Martín-García
authors.forename: Daniela
authors.initials: D
authors.lastname: Navarro
authors.forename: María S
authors.initials: MS
authors.lastname: García-Gutiérrez
authors.forename: María A
authors.initials: MA
authors.lastname: Aguilar
authors.forename: Auxiliadora
authors.initials: A
authors.lastname: Aracil-Fernández
authors.forename: Pere
authors.initials: P
authors.lastname: Berbel
authors.forename: José
authors.initials: J
authors.lastname: Miñarro
authors.forename: Rafael
authors.initials: R
authors.lastname: Maldonado
authors.forename: Jorge
authors.initials: J
authors.lastname: Manzanares
mesh_terms: D000818:Animals; D003216:Conditioning, Operant / Q000187:drug effects / Q000502:physiology; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D009538:Nicotine / Q000009:adverse effects* / Q000494:pharmacology; D009714:Nucleus Accumbens / Q000378:metabolism*; D043885:Receptor, Cannabinoid, CB2 / Q000235:genetics / Q000502:physiology*; D012054:Reinforcement, Psychology; D012201:Reward; D012646:Self Administration; D013375:Substance Withdrawal Syndrome / Q000503:physiopathology*; D017557:Ventral Tegmental Area / Q000378:metabolism*
chemical_list: D043885:Receptor, Cannabinoid, CB2; D009538:Nicotine